zumer715

A couple weeks ago my jeep started getting progressively harder to start for a couple days until it wouldn't start at all. I checked for fuel and it's getting 40 psi at the Schrader valve, I checked for spark and saw nothing so I changed the cps which had already been changed a couple months ago and still no spark. I even replaced the coil rail and I'm still getting nothing. Anybody got any ideas? I've searched and searched and it seems like everyone has solved this problem by replacing coils or cps but not me. Could it be the computer?

BruceB

Could you define "harder to start?"

Does it crank slower? Or is it taking longer for it to start at normal cranking speed?

Thanks

zumer715

it was taking progressively longer and sometimes coughed and sputtered and started rough but ran fine once started. Now there's no spark at all

BruceB

You may want to look at the camshaft position sensor and distributor. If you coil is new, then that eliminates it, you replaced the crankshaft position sensor, so it sounds like it is the camshaft position sensor that has failed.

Take my advice for what you are paying for it, I am a back yard under the tree wrencher, though I have owned my Jeep since new and do almost all my own work on it (having mechanic trust issues) lol

Turbo X_J

I checked for fuel and it's getting 40 psi at the Schrader valve
^
That's kinda low, spec should be 49 +/- 5 psi.
What are the codes?

Lake00XJ

I'm pretty sure I have a bad cps. Mine chooses when it wants to start. That would be something to check. It cranks but won't always start.

zumer715

I looked into that some but it seemed like I was finding that that wouldn't cause a no spark situation, do you think that it could?

zumer715

I was just getting 40 after priming, I wasn't able to test it with the engine actually running, not sure if the spec is different for priming?

BruceB

Cam shaft position sensors are used by the ECU to monitor the position of the cam in relation to the position of the crank shaft (monitored by the crank shaft position sensor) it's all part of the timing system of your car. If either of them goes out you can get sputtering and lurching.

zumer715

alright well then I'll check into that today. Thanks

zumer715

Well I replaced the camshaft position sensor and it started! It started up and ran great so I shut it off, took all the tools and stuff out of the engine bay and then it wouldn't start again.

After a while it finally started back up and I figured while it was running, I'd take it down to autozone to have the codes read. I didn't shut it off the whole time I was there and it idled just fine but then on my way home, it died on me and I had to get a tow home. Here are the codes I got, I know that some of them are transmission related but they were there before I swapped the trans and just haven't reset for some reason.

P0340
P0352
P0351
P0753
P0743
P0740
P0122
P0705

The guy said one of the codes meant possible bad ecu, what do you guys think?

Turbo X_J

Too much gobbletygoop, erase all that malarkey & start from scratch.

zumer715

what do you mean?

BruceB

The Electronic Control Module, or ECU as its commonly called, stores the information for your vehicle and your driving habits in its memory. The memory is maintaned by a series of capacitors that hold a charge and maintain power for the ECU when the vehicle is turned off. The following procedure will allow you to reset the memory and allow the computer to 're-learn' how to drive by adjusting to the drivers habits and the vehicles modifications.



1. Disconnect the battery by removing the positive battery cable. Remember, the positive battery cable.

2. Ground the positive cable to the negative cable for 30 seconds to erase the electric charge in the capacitors.

3. Reconnect the positive cable to the battery.

4. Turn the key to on but do not start.

5. Turn the headlights on.

6. Turn the headlights off.

7. Turn the key off.


The ECU has now been reset to its factory settings. For the next 50 warm-up periods the ECU will re-learn the engine and driving habits for your driving conditions and the newly installed parts.

Check for codes..

CCKen

All those transmission codes may be an issue with the TPS. CodeP0122 is TPS voltage low.


I would start by testing the TPS.


Chart below shows the way. Use a safety pin to back probe the wires at the TPS connector.


The P03XX codes are to do with no cam signal at the PCM and ignition coil primary circuit malfunctions (this could be a bad coil rail, which you can test as well).


TPS tests:





Coil Rail primary tests: